Peening device for tube finishing

ABSTRACT

A device having particular utility for peening and finishing the inside of a tube which comprises a rotatable shaft having at least one peening flap affixed to and extending radially from a portion of the shaft. Each such flap has peening particles mounted on the radially outer portion thereof. At least one support means is provided so as to hold the portion of the shaft having peening flaps affixed thereto in close proximity to and at a fixed distance from the wall of the tube to be peened. The device is operated, and the consequent peening action obtained by rotating or driving the shaft with a motor. As the shaft rotates, a whipping action is imparted to the flaps whereby the peening particles impinge upon the inner wall of the tube and effect the peening thereof.

United States Patent Voss et al.

[ Mar M, W72

[54] PEENING DEVICE FOR TUBE FINISHING [72] Inventors: Richard F. Voss,St. Paul; Phillip M.

Winter, White Bear Lake, both of Minn.

21 Appl. No.: 62,320

FOREIGN PATENTS OR APPLlCATlONS 113,296 5/1929 Austria ..72l53 PrimaryExaminerCharles W. Lanham Assistant Examiner-Gene 1P. CrosbyAttorneyl(inney, Alexander, Sell, Steld't & Delahunt [57] ABSTRACT Adevice having particular utility for peening and finishing the inside ofa tube which comprises a rotatable shaft having at least one peeningflap affixed to and extending radially from a portion of the shaft. Eachsuch flap has peening particles [52] "72/53 mounted on the radiallyouter portion thereof. At least one [51] Int. Cl. ..C2ld 7/06 Supportmeans is provided so as to hold the portion of the shaft 0! Search 5319, S, having peening flaps affixed thereto in cflose proximity to and/241 B at a fixed distance from the wall of the tube to be peened. The

device is operated, and the consequent peening action ob- [561'References Cit d tained by rotating or driving the shaft with a motor.As the shaft rotates, a whipping action is imparted to the flaps UNITEDSTATES PATENTS whereby the peening particles impinge upon the inner wallof 2,287,000 6/1942 Lang ..s1/241 s the tube and effect the peenmg there3,531,964 10/1970 Manning ..72/53 4 Claims, 4 Drawing Figures PEENINGDEVICE FOR 'lllUlBE FINISHING BACKGROUND OF THE INVENTION This inventionrelates to a device for uniformly peening and finishing the inside of atube.

It has long been customary to shot peen to increase fatigue strength, torelieve tensile stresses that contribute to stresscorrosion cracking, toform and straighten metal parts, etc. A detailed description of thisprocess and the materials used therein is found in the ASM CommitteeMetals Handbook", Volume 2, Eighth Division, 1964, pages 3905, andincorporated herein by reference. Prior art shot peening processes arealso described in numerous U.S. patents, e.g., U.S. Pat. No. 2,542,955and 2,982,007. In conventional shot peening, spheroidal particles ofcast steel, cast iron, glass, etc. are blown or mechanically impelled ina high velocity stream against the surface to be treated. The individualshot particles produce shallow, rounded overlapping dimples in thesurface, stretching it radially from each point of impact and causingcold working and plastic flow. The resultant compressive stress tends tocounteract tensile stresses imparted to the substrate by the precedingrolling, bending, abrading, and similar processes.

The degree of peening, which is generally expresses as peeningintensity, is a function of the weight, size, hardness and velocity ofthe peening particles, exposure time, type of substrate, angle ofimpingement, and various other factors. It is conventional to expresspeening intensity in terms of Almen arc height, according to SAE Test442, described in some detail in US. Military SpecificationMIL-S-l3l65B. In this test, a thin flat piece of steel is clamped orotherwise secured to a solid block and exposed to a blast of shot,which, as previously indicated, tends to stretch the surface, so thatthe strip will be curved when removed from the block. Test strips areSAE 1070 cold rolled spring steel uniformly hardened and tempered to ahardness of 44-50 Rockwell C, 3:0.015 inches long and 0.7450.750 inchwide. The strips are one of three thicknesses: A, 0.051 inch i 0.001; C,0.0938 inch i 0.001; and N, 0.031 inch i 0.001 inch. The height of arcof the resultant chord in inches is referred to as the Almen arc height,greater heights indicating greater peening intensity for a given teststrip thickness.

Conventional shot peening has been effective for many purposes but thereare certain applications where this process has been extremely difficultor impossible to perform. For exam ple, heretofore there has been nosimple and convenient way to peen the inside of a tube without the useof expensive, specialized equipment.

Although a unitary, portable peening wheel is described in copending USapplication Ser. No. 746,366, filed Mar. 20, 1968, such structure is notwell adapted for the peening of a tube for several reasons. For example,when the wheel is mounted on a shaft and inserted inside a tube,especially a long tube, it is extremely difficult, if not impossible, tocontrol the position of the wheel. Because the peening wheel cannot bepressed against the wall of the tube with uniform manual force, it isessentially impossible to achieve uniformity of peening. Furthermore, ifthe peening wheel is allowed to bounce about the inside of the tube, itis likely to scrape metal from the walls.

For the most part, the prior art has been limited to the use of variousabrading and swabbing materials for cleaning and polishing the inside ofa tube. For example, shafts having radially extending sandpaper or emerycloth flaps are common and are used for abrading the inside of tubes. Itis also old to employ a shaft having an eccentrically mounted head forremoving deposits from boiler tubes.

SUMMARY OF THE INVENTION This invention provides a light-weightmechanical device for peening and finishing the inside of tubes,conduits, cylinders, pipes, etc. The device is portable, simple,inexpensive and convenient to operate and yet provides a peening actionwhich is very uniform. Because even a relatively unskilled operator caneasily control the device, there is no danger of scraping metal from theinside of a tube during peening. One embodiment of the invention can beused to peen tubes which have bends or curves in them.

The simplest form of the invention comprises a rotatable shaft having atleast one peening flap affixed to and extending radially from a portionof the shaft. Each such flap comprises a flexible, tough, tear-resistantsupport member having mounted at the radially outer portion thereofparticles consisting at least predominantly of relatively smooth hardinorganic impact-resistant peening particles. At least one support meansis rotatably mounted or journaled on the shaft so as to hold the portionof the shaft having peening flaps affixed thereto in close proximity toand at a fixed distance from the wall of the tube to be peened.

The device is operated, and the consequent peening action obtained, bydriving the shaft with, e.g., an air-operated motor, an electric motor,or the like. As the shaft rotates, a whipping action is imparted to theflaps, whereby the peening particles at the radially outer portion ofthe flaps impinge upon the inner wall of the tube and effect the peeningthereof. The shaft support means holds the rotatable shaft, and thus thepeening flaps, at a fixed distance from the wall of the tube so thateach peening particle impinges upon the wall at nearly the same angle.The shaft may be rotated at any desired speed, although speeds of3,000-l0,000 r.p.m. are preferred.

In another embodiment the shaft extends through and beyond an elongatetubular sheath. At least one sheath sup port means is fixedly mounted onthe sheath near one end thereof for holding that end of the sheath inclose proximity to and at a fixed distance from the wall of a tube to bepeened. At least one peening flap is affixed to and extends radiallyfrom a portion of the rotatable shaft which extends beyond the sheath.The device of this embodiment may also be provided with a shaft supportmeans rotatably mounted or journaled on the rotatable shaft so as tohold the portion of the shaft having peening flaps afiixed thereto inclose proximity to and at a fixed distance from the wall of the tube tobe peened. Generally, the shaft support means is not required in thisembodiment unless the portion of the rotatable shaft having peeningflaps thereon is of such length that the sheath support means cannot, byitself, hold the peening flaps in close proximity to the wall of thetube to be peened. To obtain uniform peening action about the inside ofthe tube, the sheath may be slowly rotated independently of the shaft,thereby causing both the sheath and the shaft to travel around theinside of the tube at a fixed distance from the wall thereof.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described inmore detail hereinafter with reference to the accompanying drawings,wherein like reference characters refer to the same part throughout theseveral views and in which:

FIG. I is a simple form of a device made in accordance with theinvention;

FIG. 2 is a longitudinal cross-sectional view of a tube havingpositioned in the interior thereof a peening device made in accordancewith the invention;

FIG. 3 is a transverse cross-sectional view of the tube and peeningdevice of FIG. 2, taken along section line 3-3; and

FIG. 41 is a transverse cross-sectional view of the tube and peeningdevice of FIG. 2, as taken along section line 4-4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. ll there is shown asimple embodiment of a peening device 10 of the invention. A pluralityof peening flaps 10 are affixed to a portion of flexible shaft 116 andeach flap 118 comprises a flexible, tough, self-supporting,tear-resistant support member 19 having particles 20 mounted thereon atits radially outer end. It is preferred that particles 20 be locatedonly on the outer half of support member 19 for most efficient peening.Preferred support members 19 are comprised of the open mesh woven webmaterial shown and described in copending US. application Ser. No.746,366, filed Mar. 20, 1968.

Particles 20, as shown, consist at least predominantly of substantiallyspheroidal inorganic impact-resistant peening particles. Commonparticles which are useful are formed of cast steel, cast iron, tungstencarbide, and other such materials. Sintered aluminum oxide and zirconiumoxide particles are very useful, and tungsten carbide particles areespecially preferred, as peening particles. Generally, the particlesshould have a hardness of at least Rockwell C and preferably theparticles should be as hard as possible to increase their useful life.Preferably, the particles should be harder than the wall of the tube tobe peened. Friable particles are not desired because they may breakduring use. Preferably, the particles have an average diameter in therange of 0.1-2.5 mm., although smaller or larger particles be fairlyuniform in size. Particles having a surface configuration other thanspherical are also useful when the portion of the particle surface whichimpinges upon the wall of a tube has a radius of curvature in the rangeof0.l2.5 mm.

At least one shaft support means 22 is provided along shaft 16, wherebywhen device 10 is mounted in the interior of a tube support means 22holds theportion of shaft 16 having flaps 18 affixed thereto in closeproximity to and at a fixed distance from the wall of the tube. Sinceshaft support means 22 is rotatably mounted on shaft 16, it does notinterfere with the rotation of shaft 16 or flaps 18.

In FIGS. 2, 3, and 4, peening device 11, which is another embodiment ofthe invention, is disposed in the interior of cylindrical tube 50.Elongate tubular sheath 12, one end of which is being held in closeproximity to, and at a fixed distance from, the inner wall of the tube51) by sheath support means 14, has rotatable shaft 160 extendingtherethrough. Although it is not necessary to provide support meansalong the entire length of the sheath, it is desirable to provide suchmeans near the end of the sheath which is closest to the peening flaps,especially when peening long tubes. Each support means 14 is fixedlymounted or fastened to sheath 12 and may be simply a disc-shaped memberhaving a transversely bored hole adjacent a peripheral edge thereof forsheath 12 to pass through; alternatively, support means 14 may be anelongated member which is designed to hold at least the end of sheath 12in close proximity to the wall of the tube. Generally, it is preferredto make the support means out of nylon, polyoxymethylene or fluorinatedpolymers because such materials are self-lubricating, wear-resistant,non-scratching, and strong. It is desirable that support means 14 havedimensions slightly smaller than the inside diameter of the tube to bepeened (i.e., a circle circumscribing support means 14 is of a smallerdiameter than the inside diameter of the tube), so that the supportmeans will not bind in the tube when the sheath is rotated.

As in the embodiment of FIG. 1, the embodiment of FIGS. 2, 3, and 4 hasat least one peening flap 18 affixed to shaft 16, although it ispreferred to have a plurality of such flaps affixed at several locationsalong shaft 16. Preferably the peening flaps 18 are provided very closetogether along shaft 16 for most efficient and uniform peening of thetube.

Shaft support means 22 are provided at various points along shaft 16 soas to maintain said shaft and peening flaps 18 in close proximity to andat a fixed distance from the wall of the tube. Support means 22 comprisemounting portion 35 which is rotatably mounted or journaled on shaft 16,an adjustable length rod 31 connected at one end to mounting portion 35,a shank 26 mounted on the opposite end of rod 31, and wheels 24 mountedon an axle 37 which extends parallel to shaft 16 and at right anglesthrough shank 26. By means of set screw 32 and rod 31 it is possible toshorten or lengthen the long dimension of support means 22. Anotherconstruction of the shaft support means is shown as 220, where a singlewheel 24 is mounted on axle 37 disposed in a fork-shaped shank 28.Because the mounting portion 35 of each type of support means isrotatably mounted or journaled on shaft 16, said shaft may rotateindependently of support means 22 and 22a.

To prevent binding when peening device 11 travels around the inside oftube 50, a circle circumscribing support means 22 and 22a should have aslightly smaller diameter then the inside diameter of tube 50. Thus, rod31 is desirably extensible to permit adjustment of support means 22 and22a to the appropriate size, set screw 32 holding the thus-establisheddimensions. Rod 31 may also be spring loaded so that slightly ellipticaltubes may be peened with the device of the invention.

Support means 22 and 22a may be of any of several designs, e.g.,disc-shaped or elongated, and may be constructed of the same materialsas support means 14. It is important only-that support means 22 and 22abe rotatably mounted on or journaled about shaft 16 and be capable ofholding shaft 16 and peening flaps 18 in close proximity to and at afixed distance from the wall of tube 50 in such a manner that the travelof shaft 16 around the inside of tube 50 is not impeded.

In order to peen tube 50 with divide 11, one may connect an electricmotor to shaft 16 to drive it at any desired speed, preferably between3,000-10,000 r.p.m., whereby peening particles 20 on the end of peeningflaps 18 strike against the wall of the tube. As sheath 12 is rotatedslowly, support means 14, being fixedly and eccentrically mountedthereon, causes sheath 12 to travel in a path about the inside of tube50 and at a fixed distance from the wall thereof, shaft 16 alsotravelling in a similar path. Support means 22 on shaft'l6 keep theshaft, and also the peening flaps 18, in close proximity to and at afixed distance from the wall of the tube. Thus, the peening is much moreuniform than that which might be obtained with manual control of asimple rotating peening wheel or the like, where the rate of movement ofthe shaft around the wall of the tube, as well as the distance betweenthe wall and the shaft is erratic.

In order to peen tubes having curves or bends therein, shaft 16 may beprovided with a flexible joint 34. It has also been found desirable forshaft 16 and sheath 12 to be flexible so that long tubes may be peenedeasily when using a minimum of support means 14 for sheath 12. Thus, itis possible for one portion of the shaft to be flexible, e.g., portion16a which is located within sheath 12, and another portion of the shaftto be rigid, e.g., portion 16 to which the peening flaps are attached.When peening straight tubes, it has been found possible to inter-connectsupport means 22 and support means 14, e.g., by replacing axle 37 withan elongate rod of sufficient length to inter-connect support means 14and 22.

Peening flaps 18 are securely afiixed on shaft 16, as shown in thedrawings, Peening particles 20 are firmly bonded or mounted to flaps 18at the radially outer end thereof so that when shaft 16 is rotated inthe direction shown, a whipping action is obtained whereby peeningparticles 20 on the radially outer end of flaps 18 strike against thewall of the tube. It has been found that the most efiicient peening isobtained when the peening particles impinge on the wall of the tube atan angle that is as close to normal as possible. For this reason it isdesirable that peening particles 20 be located only on the outer half offlaps 18. It has also been found that the distance between shaft 16 andthe wall of the tube is important because the peening flaps l8 and thepeening particles 20 must pass therethrough without scraping the wall ofthe tube. Thus, the length of the flap 18, the flexibility of the flap,the location of peening particles 20 on the flap, and the distancebetween the flap and the wall of the tube are parameters which may bevaried so as to obtain optimum peening efi'iciency.

Generally each peening flap 18 should not be so long as to interferewith other peening flaps mounted on a common length of shaft 16. As isshown in FIG. 3, particularly where two peening flaps are mounted on acommon length of shaft 16 but at opposite sides thereof, the exposedlength of each peening flap is shorter than the circumference of shaft16. One flap will thus not interfere with the whipping action of theother flap. Preferably the length of each flap 18 is about onehalf thecircumference of shaft 16, although it is possible to use much longerflaps if the shaft is not positioned as close to the wall oftube 50 asit is shown in H6. 3. It is also possible to mount more than two peeningflaps 118 on a common length of shaft 16 if they are of such length thatthey do not interfere with each others peening action. However, thepeening flaps should not be so short that the peening intensity isdrastically reduced. For example, the peening intensity will be reducedif the flap is so short that the peening particles do not impinge uponthe wall at an angle nearly normal thereto.

We claim:

1. A device having particular utility for peening and finishing theinside of a tube, said divide comprising:

a. a rotatable shaft;

b. at least one peening flap affixed to a portion of said rotatableshaft and extending radially therefrom, each such flap comprising aflexible, tough, tear-resistant support member having mounted at theradially outer portion thereof particles consisting at leastpredominantly of relatively smooth hard inorganic impact-resistantpeening particles; and journalled on said shaft at least one shaftsupport means which holds said portion of said shaft having peeningflaps affixed thereto in close proximity to and at a fixed distancefrom'the wall of the tube to be peened; whereby when the device ismounted in the interior of a tube and said shaft is rotated, saidpeening flaps are vigorously impelled against the wall of the tube.

2. A device according to claim 1, wherein said rotatable shaft extendsthrough and beyond a sheath and is capable of turning within saidsheath.

3. A device having particular utility for peening and finishing theinside of a tube, said device comprising:

a. a sheath;

b. at least one sheath support means fixedly mounted on said sheath nearone end thereof for holding said end of said sheath in close proximityto and at a fixed distance from the wall of a tube to be peened;

c. a rotatable shaft extending through and beyond said sheath andcapable of rotating within said sheath; and

d. at least one peening flap affixed to and extending radially from aportion of said rotatable shaft which extends beyond said sheath, eachsaid peening flap comprising a flexible, tough, tear-resistant supportmember having mounted at the radially outer portion thereof particlesconsisting at least predominantly of relatively smooth hard inorganicimpact-resistant peening particles;

whereby when the device is mounted in the interior of a tube and saidshaft is rotated, said peening flaps are vigorously impelled against thewall of the tube and when said sheath is rotated said rotatable shaft ismoved around the inside of the tube and at a fixed distance from thewall thereof.

4. A device according to claim 3, wherein a shaft support means isrotatably mounted on said rotatable shaft so as to hold said portion ofsaid shaft having peening flaps affixed thereto in close proximity toand at a fixed distance from the wall of the tube to be peened.

UNITED STATES, PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,6l-8, L98 Dat d March 1 1972 Inv nt (s) Richard F. Voss and Phillip M.Winter It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

Column 3, line 17, after the word "particles" insert --could be used.Generally, the particles on a given fla should--.

Column L, line 5, the word "then" should. be changed. to ---than---.v

Singed and sealed this 15th day oi August 1972.

(S AL) Attest;

EDWARD FLETCHER: ROBERTWZOQTTSCHALK Attesting Qff l'" Commissioner ofPatents FORM Po-1050 (10-69) USCOMM-DC 60376-P69 a USv GOVERNMENTPRINTING OFFICE: 1569 O3E6-33A

1. A device having particular utility for peening and finishing theinside of a tube, said device comprising: a. a rotatable shaft; b. atleast one peening flap affixed to a portion of said rotatable shaft andextending radially therefrom, each such flap comprising a flexible,tough, tear-resistant support member having mounted at the radiallyouter portion thereof particles consisting at least predominantly ofrelatively smooth hard inorganic impact-resistant peening particles; andc. journalled on said shaft at least one shaft support means which holdssaid portion of said shaft having peening flaps affixed thereto in closeproximity to and at a fixed distance from the wall of the tube to bepeened; whereby when the device is mounted in the interior of a tube andsaid shaft is rotated, said peening flaps are vigorously impelledagainst the wall of the tube.
 2. A device according to claim 1, whereinsaid rotatable shaft extends through and beyond a sheath and is capableof turning within said sheath.
 3. A device having particular utility forpeening and finishing the inside of a tube, said device comprising: a. asheath; b. at least one sheath support means fixedly mounted on saidsheath near one end thereof for holding said end of said sheath in closeproximity to and at a fixed distance from the wall of a tube to bepeened; c. a rotatable shaft extending through and beyond said sheathand capable of rotating within said sheath; and d. at least one peeningflap affixed to and extending radially from a portion of said rotatableshaft which extends beyond said sheath, each said peening flapcomprising a flexible, tough, tear-resistant support member havingmounted at the radially outer portion thereof particles consisting atleast predominantly of relatively smooth hard inorganic impact-resistantpeening particles; whereby when the device is mounted in the interior ofa tube and said shaft is rotated, said peening flaps are vigorouslyimpelled against the wall of the tube and when said sheath is rotatedsaid rotatable shaft is moved around the inside of the tube and at afixed distance from the wall thereof.
 4. A device according to claim 3,wherein a shaft support means is rotatably mounted on said rotatableshaft so as to hold said portion of said shaft having peening flapsaffixed thereto in close proximity to and at a fixed distance from thewall of the tube to be peened.